sparc32: Limit memblock allocation to low memory

[ Upstream commit bda166930c37604ffa93f2425426af6921ec575a ]

Commit cca079ef8a changed sparc32 to use
memblocks instead of bootmem, but also made high memory available via
memblock allocation which does not work together with e.g. phys_to_virt
and can lead to kernel panic.

This changes back to only low memory being allocatable in the early
stages, now using memblock allocation.

Signed-off-by: Andreas Larsson <andreas@gaisler.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/sparc/mm/init_32.c

@@ -197,6 +197,9 @@ unsigned long __init bootmem_init(unsigned long *pages_avail)
 	size = memblock_phys_mem_size() - memblock_reserved_size();
 	*pages_avail = (size >> PAGE_SHIFT) - high_pages;
 
+	/* Only allow low memory to be allocated via memblock allocation */
+	memblock_set_current_limit(max_low_pfn << PAGE_SHIFT);
+
 	return max_pfn;
 }